diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index ebc68cd93..85fe06761 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -163,6 +163,14 @@ host port with `GBRAIN_CI_PG_PORT=5435 bun run ci:local` if 5434 collides.
 Fail-closed selector: an unmapped `src/` change runs all 29 E2E files. Hand-tune
 narrower mappings via `scripts/e2e-test-map.ts`.
 
+### PR-side security checks
+
+Besides the test gate, PRs may trigger three security workflows: Semgrep CE
+SAST (every PR — **advisory/non-blocking** while the baseline is tuned, so a
+Semgrep finding won't fail your PR), OSV-Scanner (only when `package.json` or
+`bun.lock` change), and actionlint (only when `.github/workflows/**` change).
+See `SECURITY.md` → "Automated security scanning" for details.
+
 ## Building
 
 ```bash
diff --git a/SECURITY.md b/SECURITY.md
index 833809205..da709bfd8 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -8,6 +8,30 @@ on GitHub.
 
 Do not open a public issue for security vulnerabilities.
 
+## Automated security scanning
+
+CI runs three automated security checks alongside secret scanning (Gitleaks):
+
+- **Dependency vulnerabilities** — OSV-Scanner
+  (`.github/workflows/osv-scanner.yml`) runs weekly and on any PR that touches
+  `package.json` or `bun.lock`.
+- **Static analysis (SAST)** — Semgrep CE (`.github/workflows/semgrep.yml`)
+  runs on every PR and weekly. It is currently **advisory (non-blocking)**
+  while the finding baseline is tuned; the graduation path to a blocking check
+  is documented in the workflow file.
+- **Release binary provenance** — release builds
+  (`.github/workflows/release.yml`) attest each compiled binary with
+  [GitHub artifact attestations](https://docs.github.com/en/actions/security-for-github-actions/using-artifact-attestations).
+  Verify a downloaded release binary with:
+
+  ```bash
+  gh attestation verify ./gbrain-darwin-arm64 -R garrytan/gbrain
+  gh attestation verify ./gbrain-linux-x64 -R garrytan/gbrain
+  ```
+
+All security workflows use SHA-pinned actions and least-privilege permissions,
+enforced structurally by actionlint on every workflow change.
+
 ## Remote MCP Security
 
 ### ⚠️ Do NOT use open OAuth client registration for remote MCP